Timing Belt question

[Peteric]

Hi everyone

On my 1990 se the timing belt doesn't run central on the cam gears. It runs close to the forward edge of the cam gears (about 1 to 2 mm from the edge).

It is not whining or tracking off and is not rubbing on anything and has correct tension and was changed a couple of years ago.

Is it normal not to run central on the cam gears? It runs fine on all other pulleys.

Thanks

Pete

[Vulcan Grey]

not a problem if it isn't whining, tracking off, or rubbing. It's pretty normal, but it could indicate a bit of wear on the crank bearings, they usually wear more toward the front of the engine due to the belt tension.

[MrDangerUS]

Last summer, I noticed that timing belt shifted forward and is not taut as before.

I suspected a tensioner problem(s). Last weekend, I took out the tensioner hub and bearing and discovered that the pivot stud is bent. No idea how did it happen.

Ordered a new (high alloy steel) stud from JAE. Part is high quality, made by ARP. I hope this will cure the problem.

ALSO:  IMO, in critical applications where high loads and vibration are present the nylock nuts should be avoided.
I just barely avoided a catastrophe!
Esprit 4 cyl. engines don't have a harmonic balancer, thus torque impulses are quite severe.
The source of the oscillating stresses is created by the sudden impulses from combustion gases and the inertia of the crank rotating geometry. For every combustion event the crankshaft twists and then rebounds like an elastic band. A series of these violent twisting motions occurs a number of times during one crankshaft revolution which will loosen threaded fasteners.

On my S4s, the OE Nylock nut holding timing belt tensioner hub "walked back" under hi load and vibration. That's why my belt felt suspiciously soft. I caught it just in time.

I'm replacing this critical fastener with prevailing torque all metal GM lock nut, PN# 21006320

J

[Sparky]

Done hundreds, never seen one back off, and never heard of this being an issue.

[drdoom]

I take John's remarks on inline 4 vibrations as true, having seen damage due to vibration at several points on an early Twincam in my Elan. A superior locking nut might be an improvement but I've seen studs on the same TC engine walk loose from the inlet manifold while Nylocs held. That was effectively remedied by use of longer studs on which a nut could be fitted at the far end beyond the flange, not something viable for our tensioner studs. Perhaps one of the more potent Loctite fluids instead?